JP2001333435A - Beautiful skin processing circuit and color discrimination circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a beautiful skin processing circuit and a color discrimination circuit that can accurately separate and discriminate a skin color area being an asymmetrical color space or an optional color, approximate the space with the adjustment of a few parameters together with the separation and discrimination and adjust a moving picture in real time with a reduced circuit scale. SOLUTION: The beautiful skin processing circuit comprises a skin color discrimination means consisting of an arithmetic means that translates a three- dimensional space in which a luminance signal and two color difference signals of a color image or three different RGB primary color signals exist, an arithmetic means that rotates the three-dimensional space that is translated, a means that calculates an expression of ((X/a)2+(Y/b)2+(Z/c)2)=r2, where X, Y and Z are values along the 3 axes of the rotated space and a, b and c are scale parameters of each axis, a means that discriminates the sign of the X, Y and Z to switch the scale parameters a, b and c into two kinds of parameters ap, am bp, bm, cp and cm respectively, and a linear conversion means whose input/ output characteristics are nonlinear.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technology relating to a device for handling color images, such as a video camera / television monitor / printer / image recording device.

[0002]

2. Description of the Related Art FIG. 2 shows the configuration of a beautiful skin processing circuit.

In this skin color processing circuit, a luminance signal Yi [2-7] of a color image, a color difference signal Cb [2-8],
Cr [2-9] is input to the skin color determination circuit [2-2],
The skin color discrimination circuit [2-2] outputs a skin color intensity value f, which is a signal whose value increases as the color approaches the skin color. The luminance signal Yi [2-7] is also converted to a smoothing filter [2-1].
, And the smoothing filter [2-1] creates and outputs a luminance signal with attenuated high-frequency components and little detail components. The multiplier [2-5] multiplies the output of the smoothing filter [2-1], which is the luminance signal with the reduced detail component, by the skin color intensity value f. Also, from the skin color intensity value f, (1
The coefficient subtracted by the subtraction circuit [2-3] of -f) and the luminance signal input Yi [2-7] are multiplied by the multiplier [2-4]. Finally, these two multipliers [2-5], [2-
4] The outputs are added by an adder circuit [2-6], and Yo [2-10] is output as a luminance signal subjected to skin-smoothing processing.

Here, the output Yo [2-10] is represented by Yo = f × ([2-5] output) + (1-f) × Yi. When the skin color intensity value f is small, the component of Yi is In many cases, when the skin color strength value f is close to 1, the luminance component in which the detail component is attenuated and the skin roughness is reduced is increased, so that the luminance obtained by removing the skin roughness only on the part of the human skin A signal is created to obtain the effect of the beautiful skin processing.

The prior art is described in the embodiment of Japanese Patent Application Laid-Open No. 6-105323 with respect to the skin color discriminating circuit. FIG. 6 illustrates the method of this publication.

That is, after the RGB input is subjected to IQ conversion by the matrix circuit [6-1], the adder [6-]
2] and [6-3], the coordinate origins of the I and Q axes are moved.
The coordinate-converted I and Q signals are used for an absolute value calculation circuit [6-4].
The absolute value is calculated in [6-5], and the multiplier [6-6],
After the coefficient is multiplied in [6-7], the adder [6-
8], it is subtracted from the R _{The set} at [6-9]. This process can be expressed as

F _out = R _set −K 1 (I−I _set ) −K 2 (Q−Q _set ) After that, the negative clip circuit [6-10] sets [6
-11]. Area of skin color intensity values becomes a bottom surface area of the "square Sui" figure also skin color intensity values, etc. proximal surface is a "square Sui" surrounded by plane as the [6-11], I _{se The} characteristic becomes symmetrical in the I and Q directions with respect to _t and Q _set .

In another embodiment of the skin color discriminating circuit, data of each address is stored using a memory in which three signals of R / G / B or Y / RY / BY are assigned to three-dimensional addresses. There is a method of storing a skin color intensity value.

[0009]

SUMMARY OF THE INVENTION As described above, in a beautiful skin processing circuit having a function of reducing a detail component of the skin such as a person's face reflected in a color image to clearly project the person, a circuit for discriminating the skin color is used. Is provided.

However, in the conventional skin color discriminating circuit, as described above, when the skin color region of the color space is cut out, the skin color region is represented by a space obtained by cutting the skin color region in a plane from the circuit scale, or the space is symmetric. Although it is assumed that the actual skin color area is asymmetrical as a color space and has a curved surface, an error occurs between the cut skin color area and the actual skin color area, and Judgment cannot be performed accurately. Therefore, the effect of the beautiful skin treatment was not sufficiently exhibited because the beautiful skin treatment was not performed accurately.

In some cases, a memory is used as a circuit for accurately determining a flesh-color area. However, if the coordinates in a three-dimensional color space are represented by 8-bit data and the discrimination signal is represented by 8-bit data, 25 bits are used.
6 ³ × 8 = 134217728 bits, which increases the circuit scale.

Also, it is necessary to set the skin color discrimination data for each point (256 ³ = 16777216 places) in the ^three -dimensional space, and it is very difficult to set the discrimination data.

Further, when a moving image such as a video camera, whose photographing conditions change every moment, is adjusted in real time in accordance with the photographing conditions, it is necessary to have a plurality of memories prepared in advance for each condition, thereby increasing the circuit scale. Becomes difficult.

In addition to the skin color determination circuit of the beautiful skin processing circuit, a circuit for determining an arbitrary color other than the skin color of a color image also includes
The same problem as described above occurs.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and it is possible to accurately separate and discriminate a flesh color region or an arbitrary color which is an asymmetrical color space. An object of the present invention is to provide a beautiful skin processing circuit and a color discrimination circuit that can reduce the circuit scale by approximating a space by parameter adjustment and can adjust a moving image in real time.

[0016]

The present invention has the following configuration in order to solve the above-mentioned problems. The present invention provides a skin-skin processing circuit that determines a flesh-color portion of a color image and adjusts the frequency band of the detail component of the flesh-color portion of the image based on the discrimination signal to reduce the roughness of the human skin in the color image and project the image. A computing means for translating a three-dimensional space spanned by three different signals of a luminance signal of a color image and two color difference signals or three different primary color signals of RGB; a computing means for rotating the translated three-dimensional space; Using the scale parameters a, b, and c of each axis for the values X, Y, and Z of the three axes in the

(Equation 3) And scale parameters a, b, and c are determined by determining the signs of X, Y, and Z.
means for switching to p, am, bp, bm, cp, cm;
A beautiful skin processing circuit comprising a skin color discriminating means constituted by a one-dimensional conversion means having a non-linear input / output characteristic.

According to the present invention, in a circuit for judging a skin color of a beautiful skin processing circuit having a function of clearly displaying a person by reducing skin detail components such as a person's face reflected in a color image, a luminance signal and two color differences The arithmetic means for translating the three-dimensional space spanned by the three different signals of the signals or the three primary color signals of RGB converts the coordinates to the flesh color center of the color space, and the arithmetic means for rotating the three-dimensional space translated further. After adjusting the coordinate axes of the flesh color space, X, Y, and Z values of the three axes of the rotated space are expressed as X,
Using the scale parameters a, b, and c of each axis that are switched by the signs of Y and Z

(Equation 4) Is calculated so that r is centered on the origin of the coordinates (X, Y, Z).
^2. Create skin color space data in which the coordinated surface of ² is an asymmetric elliptic surface, and convert the skin color space data to a non-linear 1
A skin color intensity value for adjusting a detail signal of a skin color portion of an image is created by inputting the signal to a dimension conversion unit.

According to the present invention, as described above, the skin color area, which is an asymmetric color space, can be accurately separated and discriminated, and the space can be approximated by a small number of parameter adjustments, thereby reducing the circuit scale. In addition, it is possible to adjust a moving image in real time.

According to the present invention, there is provided a color discriminating circuit for discriminating an arbitrary color (preferably having an asymmetrical color space) of a color image, wherein a luminance signal of the color image and two color difference signals or an RGB signal are provided. A computing means for translating the three-dimensional space spanned by three different signals of the three primary color signals, a computing means for rotating the translated three-dimensional space, and values X, Y, and Z for each of the three axes of the rotated space Using the scale parameters a, b, and c of each axis

(Equation 5) And scale parameters a, b, and c are determined by determining the signs of X, Y, and Z.
means for switching to p, am, bp, bm, cp, cm;
A color discriminating circuit comprising one-dimensional conversion means having a non-linear input / output characteristic.

According to the present invention, in a circuit for determining an arbitrary color, a luminance signal and two color difference signals or RG
The arithmetic means for translating the three-dimensional space spanned by three different signals of the three primary color signals B converts the coordinates to the arbitrary color center having an asymmetrical color space, and further rotates the translated three-dimensional space. After adjusting the coordinate axes of an arbitrary color space by the arithmetic means, the scale parameters a, b, and b of the respective axes switched by the signs of X, Y, and Z with respect to the values X, Y, and Z of the three axes in the rotated space. using c

(Equation 6) Is calculated so that r is centered on the origin of the coordinates (X, Y, Z).
^2. Create arbitrary color space data in which the coordinated surface of ² becomes an asymmetrical elliptic surface, and input the skin color space data to the one-dimensional conversion means whose input / output characteristics are non-linear. Create a skin color intensity value for adjustment.

According to the present invention, as described above, an arbitrary color area can be accurately separated and discriminated, and a space can be approximated by a small number of parameter adjustments. This allows adjustment in real time.

The principle of the present invention will be described. As an example, a description will be given of a skin color intensity value in a color space in a three-axis vector space of luminance (Y) and color difference signals Cb and Cr. The same applies to any color having an asymmetric color space.

Here, the color difference signals Cb, Cr and B-
Since Y and RY can be respectively converted by appropriate gain adjustment and linear conversion by rotation, it is equivalent to replace the color difference signals Cb and Cr with the color difference signals BY and RY.

FIG. 7 shows a YCC space in which the vertical axis represents luminance (Y) and the horizontal direction represents a vector plane of color difference signals Cb and Cr.

The center of the flesh color is located substantially on the I axis on the color difference signal Cb, Cr vector plane, and is distributed in the saturation direction of the vector according to the density of the flesh color and in the Y direction according to the luminance value.
There is some swelling in the Q-axis direction due to the color temperature of the light source and the reflected light from other subjects, and distribution is asymmetric in the I-axis direction and the Y-axis direction.

Therefore, as shown in FIG. 7, a coordinate conversion of (x, y, z) is performed from the coordinate axis of (Cb, Cr, Y) with the point considered to be the center of flesh color as the origin, and (x, y, z)
The skin color region is separated in a space where the asymmetrical elliptical curved surface is the coordinate surface on the coordinates.

According to the value of r corresponding to the distance from the center calculated by the asymmetric elliptic operation, when r is small, 1
A skin color intensity value is obtained from a non-linear characteristic curve that becomes 0 as the size increases.

FIG. 8 is an explanatory diagram of the coordinate conversion. The coordinate conversion process is as follows: A parallel movement is performed on (Cb, Cr, Y) to the center of the flesh color (point P in FIG. 8A). 2. The Cb and Cr axes are rotated around the point P, and the coordinates are converted to I / Q axes. 3. Since the z-axis has a slope in the positive direction of the I-axis with respect to the Y-axis according to the Y signal value as shown in FIG.
As shown in (b), the Y-axis and the I-axis are rotated around the Q-axis to create the z'-axis and the y'-axis of the (x ', y', z ') coordinates. Note that the x 'axis coincides with the Q axis. 4. Finally, as shown in FIG. 8C, the z 'axis and the x' axis are rotated about the y axis to create the z axis and the x axis of the (x, y, z) coordinates. Note that the y axis coincides with the y 'axis.

In FIG. 8A, (Cb, Cr, Y)
The unit vector of each axis is E_b/ E_r/ E _y, Q / I axis unit
Vector E_q/ E_iThen

(Equation 7)

In FIG. 8B, (x ', y', z ')
When the unit vectors of each axis of the _{E 'x / E' y /} E 'z,

(Equation 8)

In FIG. 8C, if the unit vector of each axis of (x, y, z) is E _x / E _y / E _z ,

(Equation 9)

[0032] (Cb, Cr, Y) on the coordinate, the coordinate values of the skin color center (P _{point) (P b, P r,} P Y), any color (C
Assuming that the coordinate value of (point) is (C _b , C _r , C _Y ), (x,
y, z) Coordinate value of point C on coordinates (C _x , C _y , C _z )
Is

(Equation 10)

[0033] _{Thus, (C x C y C z} ) = (C b -P b C r -P r C Y -P Y) · A · B · C ... formula by (x in (1), y, z ) Can be performed.

The equation of the elliptic curved surface shown in FIG.

[Equation 11] And x, y, z coordinate axes and ± a, ± b,
Intersects the point ± c.

From this equation

(Equation 12) think of.

When a, b, and c are fixed and r ² is obtained for an arbitrary point (x, y, z),

(Equation 13) Which are the x, y, z coordinate axes and ± ar, ± br,
An elliptical curved surface similar to the ellipse of the formula (2A) crossing at a point of ± cr is obtained. Therefore, r indicates the size of the elliptical curved surface, and can be considered as a value corresponding to the distance from the center P point of an arbitrary point (x, y, z).

From the above, the coordinate values (x,
When the value of r is obtained by performing the calculation of the expression (2B) on (y, z), a distance having anisotropy from the center P point in each coordinate axis direction is obtained.

The elliptical surfaces obtained by the equations (2A) and (2B) have anisotropy with respect to the x, y, and z axes, but are symmetric with respect to the positive and negative directions of the axes.

Then,

[Equation 14] And the values of a, b, and c are defined as ap, am,
By switching to bp, bm, cp, cm, FIG.
An asymmetric elliptical curved surface as shown in (b) can be obtained.

By performing the above calculation, a value r corresponding to the distance from the center of the flesh color is obtained, and using this r, a flesh color intensity value is obtained from a flesh color intensity table which is a non-linear conversion characteristic shown below. Here, the input to the nonlinear characteristic is not r, but r
^{Assume 2} . This is because both r and r ² are monotonically increasing, and it is possible to incorporate the square root operation characteristic of r ² in the non-linear characteristic, thereby reducing the square root operation circuit.

From the value of r ² obtained by the elliptic surface calculation,
The skin color intensity value is obtained from the characteristic of the nonlinear curve as shown in FIG.

By moving the nonlinear curve to the right as shown in FIGS. 10 (a) and 10 (b), the skin color region to be detected can be widened. In addition, according to the above-described method of calculating r in the elliptic surface calculation, the distribution of the flesh color intensity value becomes steeper as the values of a, b, and c are smaller.

[0043]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a configuration of a skin color determination circuit according to the embodiment. As shown in FIG. 1, the skin color determination circuit mainly includes a coordinate conversion unit [1-1], an elliptic surface calculation unit [1-2],
It has a non-linear converter [1-3].

The coordinate conversion unit [1-1] in FIG. 1 receives the luminance signal Yi and the color difference signals Cb and Cr, and performs the process of moving and rotating the origin of the coordinates in the color space shown in FIG. The coordinate-transformed data is obtained by the elliptic surface calculation unit [1-2] in FIG.
The calculation of the asymmetrical elliptical surface shown in (1) is performed, and the square value r ² of the distance from the center of the skin color is created.

Next, the nonlinear conversion section [1-3] shown in FIG.
Skin color from r ² by a nonlinear characteristic shown in intensity value f [1-
7] is output.

FIG. 3 shows details of the configuration of the coordinate conversion unit [1-1] of FIG. The parameters Py [3-4], Pb [3] are used to move the origin of the coordinates to the input luminance signal Yi and color difference signals Cb, Cr of the color image.
−5] and Pr [3-6] are added to adders [3-1] and [3]
-2] and [3-3]. Then, the parameters [3-7], [3-8], [3-3] for rotating the coordinate axes by the multipliers [3-10], [3-11], [3-12]
−9] is multiplied by the outputs of the adders [3-1], [3-2] and [3-3] to perform coordinate conversion, and output pixel data (x, y, z) subjected to coordinate conversion. Is done.

Here, parameters [3-7] and [3-
8] and [3-9] include A ·
A 3 × 3 matrix operation result of B · C is stored.

FIG. 4 shows the elliptic surface calculation unit [1-2] of FIG.
3 shows the details of the configuration. An asymmetric elliptic surface calculation is performed on the coordinate-transformed input data (x, y, z).

The input data x [4-20], y [4-2]
1], z [4-22] for the sign determination circuit [4-
1], [4-7], and [4-12], the signs of x, y, and z are determined. When the sign is positive, the selector [4-4],
In [4-10] and [4-16], the parameter ap [4-
2], bp [4-8] and cp [4-14] are selected. In the case of a negative value, the parameters am [4-3], b
m [4-9] and cm [4-15] are selected. In the dividers [4-5], [4-11], [4-17], x, y,
Selectors [4-4], [4-10], [4-
16] is divided.

The divided dividers [4-5] and [4-1]
1] and [4-17] are output from the divider [4-6],
Squared in [4-12] and [4-18]. further,
The squared 3 signal data are added by the adder [4-19], the value of r ² represented by the above formula (2B) is calculated and outputted.

FIG. 5 shows the details of the configuration of the non-linear converter [1-3] of FIG. Here, as an example,
FIG. 11 shows a configuration in a case where the nonlinear characteristic of FIG. 10 is approximated by a three-fold line.

Registers [5-4], [5-5], [5-
6] and [5-7] store the x-coordinate values of the end points of the polygonal line, and [5-19], [5-20], [5-2]
1] and [5-22] store the y-coordinate values of the end points of the polygonal line. Also, [5-14], [5-15], [5
-16] and [5-17] store values indicating the inclination of the polygonal line. Expressing the nonlinear characteristic approximated by this broken line by an equation,

(Equation 15)

Where

(Equation 16) And

[0054] The output r ² of the elliptic surface calculation of FIG. 4 is a comparator [5-8], [5-9], [5-10], [5-11]
In registers [5-4], [5-5], [5-6],
It is compared with the x-coordinate value of x _i in [5-7].

The result is decoded by the decoder circuit [5-12], and the selector [5-1] for selecting a parameter is used.
3], [5-18], and [5-23] are generated. X _i the selector [5-13] by the output of the decoder circuit [5-12], a _i the selector [5-18], y _i is selected by the selector [5-23]. After being subtracted from r ² x _i by the subtractor [5-1], a _i is multiplied by the multiplier 5-2, further adder [5-
3], y _i is added, and finally a subtractor [5-24]
Is subtracted from 1 to perform the processing of Expression (5-1), and the skin color intensity value f is output. Although the number of polygonal lines is three in this case, x _i, a _i, a y _i register selector [5-13], [5-18], [5-23]
The number of polygonal lines can be easily increased by increasing the number of input ports.

[0056]

According to the present invention, a skin color region which is an asymmetric color space in a circuit for determining a skin color of a beautiful skin processing circuit which cleans a person by reducing skin detail components such as a person's face reflected in a color image. Can be accurately separated and discriminated, and the space can be approximated with a small number of parameter adjustments, thereby reducing the circuit scale and realizing a beautiful skin processing circuit that can adjust video in real time. Become.

The skin color discriminating circuit can discriminate not only a flesh color but also an arbitrary color space, and is used as a circuit for discriminating a specific color such as a circuit for improving color reproducibility in a function for handling a color image. Can be used.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a configuration of a skin color determination circuit according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a configuration of a beautiful skin processing circuit.

FIG. 3 is a detailed explanatory diagram of a coordinate conversion unit in FIG. 1;

FIG. 4 is a detailed explanatory diagram of an elliptic curved surface calculation unit in FIG. 1;

FIG. 5 is a detailed explanatory diagram of a nonlinear conversion unit in FIG. 1;

FIG. 6 is an explanatory diagram of a conventional example of a skin color determination circuit.

FIG. 7 is an explanatory diagram of a color space.

FIG. 8 is an explanatory diagram of coordinate conversion.

FIG. 9 is an explanatory diagram of characteristics of an asymmetric elliptic surface calculation.

FIG. 10 is an explanatory diagram of characteristics of nonlinear conversion.

[Explanation of symbols]

 1-1 Coordinate conversion unit 1-2 Elliptic surface calculation unit 1-3 Nonlinear conversion unit 1-4 Luminance signal input: Yi 1-5 Color difference signal input: Cb 1-6 Color difference signal input: Cr 1-7 Skin color intensity value output : F

Continued on front page F-term (reference) 5B057 AA11 CA01 CA08 CB01 CB08 CE01 CE18 5C066 AA01 AA03 AA05 AA06 BA20 CA05 GA01 GA02 GA05 KD06 KE01 KE02 KE03 KE04 KF05 KG01 KL13 5C077 MP08 PP19 PP31 PP32 P04P37 PP31 PP32 PP04 HPP HB05 HB11 LA02 LA15 LA31 LB01 MA11 NA03 NA07 NA09 NA11 NA15 NA29

Claims (2)

[Claims] 1. A skin-smoothing circuit for determining a flesh-color portion of a color image and adjusting a frequency band of a detail component of the flesh-color portion of the image based on the discrimination signal to reduce rough skin of a person in the color image. Image luminance signal and two color difference signals, or RG
Computing means for translating the three-dimensional space spanned by three different signals of the three primary color signals of B; computing means for rotating the translated three-dimensional space; and values X and Y for each of the three axes of the rotated space , Z using the scale parameters a, b, c of each axis. And a scale parameter a, by determining the sign of X, Y, Z.
b and c are respectively set to two kinds of parameters ap, am, bp, b
A beautiful skin processing circuit comprising: means for switching to m, cp, cm; and skin color discriminating means constituted by one-dimensional conversion means having non-linear input / output characteristics. 2. A color discriminating circuit for discriminating an arbitrary color of a color image, comprising: a luminance signal of the color image and two color difference signals;
Computing means for translating the three-dimensional space spanned by three different signals of the three primary color signals of B; computing means for rotating the translated three-dimensional space; and values X and Y for each of the three axes of the rotated space , Z using the scale parameters a, b, c of each axis. And a scale parameter a, by determining the sign of X, Y, Z.
b and c are respectively set to two kinds of parameters ap, am, bp, b
A color discriminating circuit comprising: means for switching between m, cp, and cm; and one-dimensional conversion means having non-linear input / output characteristics.